I have had my house since 2005. Nobody informed me, nor did I notice, several "obvious" problems with the house, including the "professional" inspector. The primary structural problem is that the foundation of the original house is rubble and the central support beam is rotted. A notch was left in the foundation for the central beam which is mostly rotted off on both ends. In addition, a large notch was cut in the beam for furnace duct work. There are 2 adjustable metal jacks supporting the beam at each end and a half log wedged beneath the middle of the beam. All 3 sit directly on the concrete basement floor. I think I should add another adjustable metal jack to replace the log. I don't know whether or not to be concerned about the situation or not. Any and all responses will be appreciated. Thank you.

Sounds like a temp fix to fix a temp fix. The floor was never designed to carry the load that is now carrying. The floor is doing the job but it is chancy, I think you might be better to build a wall so the load would be better spread out.
To do the posts right you would want to put footings under each post and then change to a more perminent post design.